Humanity currently faces enormous political and scientific challenges in identifying and securing stable future sources of renewable energy in an environmentally acceptable and sustainable manner (e.g., leading to so-called biofuels/bioenergy). Similar concerns and considerations also apply to the continued future supply of other key petrochemical intermediates, such as monomers needed for sufficient levels of industrial polymer production (e.g., polystyrenes, polyethylenes, etc.) as well as for stable sources of key specialty chemicals (e.g., flavor and fragrance chemicals, which at present are produced in regions of varying political stability, and which can also be subject to seasonal (climatic) variations; such factors often result in unpredictable market prices for these commodities). This is not a new scientific problem, but rather reflects one that has been difficult to solve over a period spanning more than three decades, until now again brought to the forefront by the most recent biofuels/bioenergy crisis. Today, about 12% of all the petroleum resources are used for non-fuel/non-energy purposes, this including polymer and other specialty chemical applications.
The so-called ‘lignin problem’ or challenge. To date, the difficulties in plant biomass utilization have centered on the recalcitrance of the various lignocellulosic matrices present in (woody) plants; namely, the so-called ‘lignin problem’ or challenge. Lignins are monolignol-derived polymeric end-products of the phenylpropanoid pathway (originating from the amino acids phenylalanine and tyrosine). From a structural perspective, the lignins, Nature's second most abundant organic substances after cellulose, are amorphous plant cell wall polymers that make up ca 20-30% of all plant stem biomass.10,11 More specifically, vascular plant species have differing lignin contents, with values ranging from ˜30% in conifers (softwoods) to lower amounts (˜20-25%) in hardwoods (such as poplar) and herbaceous plant species, to even smaller levels in various primitive plant species. The physiological roles of lignins are to engender structural support to the vascular apparatus, thereby enabling such organisms to stand upright, as well as providing conduits for water and nutrient transport, and to provide physical barriers against opportunistic pathogens. Particular actual (i.e., minimal) lignin contents and/or compositions may be needed for a particular plant to avoid any deleterious effects for growth/development/stem structural integrity, etc. In general, lignins represent a formidable technical challenge, particularly due to their intractable nature, for improved plant biomass utilization, e.g., when considering the use of woody biomass for bioethanol production, as well as for wood, pulp and paper manufacture.
More specifically, there are two major scientific hurdles that have not been technically overcome for the facile utilization of this and other plant renewable resources, both of which involve the polymeric lignins.
The first results from their intractable nature, since lignin removal has long been a limitation in the processing of wood for both pulp/paper manufacture and for forage digestibility by ruminants. This is largely due to the lack of isolated enzymes and/or proteins that can efficiently degrade lignin macromolecules, in contrast to reports in the nineteen-eighties that indicated this problem had been solved.3-6 That is, nearly twenty years ago, it was reported that several productive routes for lignin removal from wood had both been discovered and attained via utilization of lignin-degrading enzymes in fungi/bacteria, and where three candidates ultimately emerged (lignin peroxidase, manganese peroxidase and laccase). However, this “lignin peroxidase” or “ligninase”6 was only assayed initially with an aqueous acetone extract of spruce wood,3 which does not actually extract the lignins from wood. Twenty years later, none of these enzymes are (routinely) utilized in biotechnological applications for lignin removal/separation, and their roles in enzymatic lignin biodegradation are still in question, as we had noted earlier.7 Today, more than 50 million tons of lignin-derived substances are generated annually as by-products of pulp/paper manufacture within the USA alone.8 Other possibilities now being considered are the putative true lignin depolymerases that target specific inter-unit linkages in lignin macromolecules.9 
The second technological hurdle is that lignins cannot readily be converted into either ethanol and/or other liquid/gaseous fuels using currently available fermentation processes. Indeed, the polymeric lignins themselves are a formidable physical barrier to an efficient fermentation of carbohydrate biomass for ethanol generation, and thus their presence represents a critical problem in making these technologies more economical.
There is therefore, an urgent need in the art for highly creative and sound technological solutions for renewable (plant) resource utilization.
There is therefore, a pronounced need in the art for an approach whereby the carbon allocated towards lignification is redirected, to provide for inherently more useful and/or more easily tractable materials, and to facilitate the generation of, for example, biofuels from the remaining plant biomass.